The present relates to the manufacture of a tubular liner for use in softlining pipe rehabilitation. Various softlining methods of rehabilitating a pipe conduit which is buried underground are known. Generally speaking, such methods involve the use of a flexible lining hose which is subsequently converted into a rigid pipe liner by use of thermosetting resins. The flexible lining hose or tube generally has a diameter which is slightly smaller than the inner diameter of the pipe conduit to be repaired.
One such softlining method is shown in U.S. Pat. No. 4,064,211 in which a lining hose is everted into the pipe conduit to be rehabilitated. In this method the lining hose is introduced into the interior of the pipe conduit by turning one end region over the other and by causing the turned over region to gradually advance into the interior of the pipe conduit. This process is called eversion. During the performance of this step, the resin soaked layer which is originally located at the interior is gradually transferred to the exterior of the lining hose. Relatively high forces are needed for the gradual turning over of the lining hose owing to the expansion work to be performed at the turned over region.
Another softlining method is described in U.S. Pat. No. 4,770,562. In that patent, the evertible lining hose is referred to as an auxiliary hose and is generally comprised of plastic materials. In such a softlining method, the auxiliary hose is everted using high water pressure within a collapsed resin-absorbent liner. After the auxiliary hose is everted to expand the collapsed liner, the auxiliary hose is removed from the pipe conduit. This auxiliary hose is then reused to expand another section of collapsed resin absorbent liner.
When a liner or tube is used to expand a collapsed liner in this manner, the tubular liner must be strong enough to maintain its integrity under the pressures created by eversion process and not allow leakage of fluid through the seam of the tubular liner.
In each of the methods described above, the construction of the seam of the tube or liner is important. If fluid leaks through the seam a substantially poorer structure results upon curing of the resin. For example, if the tubular liner is resin-impregnated and everted using water, it is important that the water not leak through the seam of the tubular liner. If the water contacts the resin, it impairs the curing ability of the resin.
U.S. Pat. No. 4,446,181 also describes the manufacture of tubular laminates which are useful in softlining pipe rehabilitation methods. Those tubular laminates are made by stitching together the butted edges of a flat web formed from a resin-absorbing layer, on one side of which is an impermeable layer. Once sewn in a tube configuration, a sealing ribbon or coating is applied on the outside of the tubular laminate over the stitching to prevent leakage through the stitching holes during installation.
The present invention provides a new and improved tubular liner and method of forming tubular liners for use in softlining pipe rehabilitation. The present invention provides a tubular liner which can withstand multiple eversions by high pressure fluid without leakage or rupture.